It could be the HomeKit Adaptive Lighting feature that would have been available with an update to your Hue lighting?
I did receive a similar alert but chose to ignore it, I then wanted to find out more but wasn’t sure what to look for. It looks like you can add the adaptive lighting to a scene or a bulb, the article above explains what to look for.
If it’s not that then in the Hue app you can check for routines from other apps in the Routines tab. This is where a third party app can add something to the hub, I have one that I use as an alarm that flashes a set of lights.
Have a look in Shortcuts in the Automation tab to see if you have anything that is set up in the ‘My Home’ section, I have a few routines that switch on and off the outside lights, and the lounge lights in the afternoon etc.
Good luck, I have had to do this for my parents a few times when their automations fail, I’ve slowly eliminated all the third party apps and managed to get most things done in Shortcuts.